The present invention relates to a chuck for attaching and removing a saw blade to the tool shaft of a power saw, and more particularly to a keyless saw blade chuck for securing the saw blade to the tool shaft of the saw.
Different types of saw blade chucks have been employed in the past. One well-known type includes a threaded set screw which secures the blade either by clamping the blade to the tool shaft or by passing the screw through a mounting hole in the saw blade directly into the tool shaft. This type of apparatus requires a key to release and insert the saw blade into the chuck.
Other chucks do not require a key or other tool. One such chuck is disclosed in U.S. Pat. No. 4,106,181 and has a camming member to hold a saw blade against the tool shaft. The camming member engages the saw blade either directly or by means of an intermediate member. The chuck also has a pin for preventing relative axial movement of a saw blade and the tool shaft, and a shaft aligned with a notch on the received saw blade. The pin is aligned with and projects slightly into a hole in the received portion of the saw blade. This chuck also includes a lock mechanism to retain the camming member in a closed or blade holding position while the saw is in use.
Another type of keyless saw blade chuck is disclosed in U.S. Pat. Nos. 4,594,781 and 4,470,196. This type of chuck, however, merely holds the blade by clamping. Given the axial reciprocation of the tool shaft, the blade may tend to slip out of the chuck during use.
Still another type of keyless saw blade chuck is disclosed by U.S. Pat. No. 3,823,473. One embodiment of the chuck comprises a member carrying an axially slideable sleeve. The member provides a pair of spaced apart pins which mate with a pair of holes in the mounting end of the saw blade. The sleeve provides grooves for receiving the pins, and is biased by a spring into a closed position in which the sleeve covers and holds the mounting end of the saw blade on the pins.
The chucks described above are deficient in different manners. Chucks of the type utilizing a set screw are prone to problems such as the screw vibrating loose during use or the loss of the key necessary to loosen the set screw for insertion or removal of a saw blade. As noted above, chucks of the type utilizing a camming member and lock mechanism can be susceptible to the saw blade sliding out of the holder or to failure of the lock mechanism. Moreover, these chucks do not adequately allow for saw blades of different thicknesses. It would be advantageous to have a device which overcomes these problems.
It is accordingly an object of the present invention to provide a chuck for attaching a saw blade to a tool having an axially reciprocating tool shaft which eliminates the need for a separate key to remove or to attach a saw blade to the tool shaft. It is also an object of the present invention to provide a chuck which securely holds an attached saw blade in such a manner that the blade cannot slip out of the chuck while in use. It is a further object of the present invention to provide a chuck which is capable of receiving saw blades of various thicknesses.